Collect. Czech. Chem. Commun. 1992, 57, 2383-2399

Conformation Dependent Cyclizations of 1,3,3,5-Tetraphenylpentane-1,5-dione

Pavel Šebeka, Jiří Novotnýb, Bohumil Kratochvílb, Marián Schwarzc and Josef Kuthana

a Department of Organic Chemistry, Prague Institute of Chemical Technology, 166 28 Prague 6
b Department of Solid State Chemistry, Prague Institute of Chemical Technology, 166 28 Prague 6
c Institute of Hygiene and Epidemiology, 965 01 Žiar nad Hronom


The molecular and crystal structure of 1,3,3,5-tetraphenylpentane-1,5-dione (I) obtained from direct methods and anisotropically refined by the least-squares method shows that the two 3,3-phenyl groups force the molecule into a conformation suitable for formation of cyclic products and intermediates. Compound I crystallizes in P1 group with lattice parameters a = 8.444(1), b = 10.195(2), c = 14.618(2) Å, α = 75.52(2)°, β = 73.22(1)°, γ = 65.47(1)°. Photochemically and thermally found was the system III. The reaction of 1,5-dione I with phenylmagnesium bromide gives the 2,3-dihydropyran derivative III, whereas complex hydrides give a mixture of IV and VI. On treatment with magnesium, the diketone I gives diol VIII. Chlorine (Cl2) reacts with compound I to give the mono-, di-, and tetrachloro derivatives XII, XIII, and XIV, respectively. Bromine (Br2) produces 3,5-dibromo-4H-pyran derivative XVIII, whereas I2 only catalyzes the formation of 4H-pyran V. The formylation of dione I with dimethylformamide and POCl3 gives the 4H-pyran-3-carbaldehyde XX. Probable mechanisms of the reactions investigated and the stereochemistry of compounds VI, VIII, XIII, and XIV are discussed.